Ai giúp em đc ko ạ xin chân thành cảm ơn

`@` lg

`a)` `3/14 + -15/14 = (3 + -15)/14`

`=` `-12/14`

`=` `-6/7`

`--`

`b)` `-2/7 - 15/34 = -68/238 - 105/238`

`=` `-173/238`

`--`

`c)` `5/17 + -15/34 . 2/5 = 5/17 + -3/17`

`=` `(5 + -3)/17`

`=` `2/17`

`--`

`d)` `1/2 . 5/6 + 2/3 . 3/4 = 5/12 + 1/2`

`=` `5/12 + 6/12`

`=` `11/12`

`--`

`e)` `-7/8 : 21/16 - 5/3 . (1/5 - 7/10) = -7/8 : 21/16 - 5/3 . -1/2`

`=` `-2/3 - 5/3 . -1/2`

`=` `-2/3 - -5/6`

`=` `1/6`

`--` 

`f)` `1/5 (1/2 - 1/3) : (-9/10) + -7/3 = 1/5 . 1/6 : (-9/10) + -7/3`

`=` `1/30 : (-9/10) + -7/3`

`=` `-1/27 + -7/3`

`=` `-64/27`

`**`

Bài `3`

`a)` `2/3 + (5/7 + -2/3)`

`=` `2/3 + 5/7 + -2/3`

`=` `(2/3 + -2/3) + 5/7`

`=` `0 + 5/7`

`=` `5/7`

`--`

`b)` `1/5 . 4/7 + 3/7 . 1/5 - 1/5`

`=` `1/5 . (4/7 + 3/7) - 1/5`

`=` `1/5 . 1 - 1/5`

`=` `1/5 - 1/5`

`=` `0`

`--`

`c)` `-1/9 . -3/5 + 5/-6 . -3/5 - 7/2 . 3/5`

`=` `1/9 . 3/5 + 5/6 . 3/5 - 7/2 . 3/5`

`=` `3/5 . (1/9 + 5/6 - 7/2)`

`=` `3/5 . (-23)/9`

`=` `(3 . (-23))/(5 . 9)`

`=` `(-23)/(15)`

`--` 

`d)` `5/13 + -7/6 + -20/41 + 8/13 + -21/41`

`=` `(5/13 + 8/13) + [(-20/41) + (-21/41)] + (-7/6) `

`=` `1 - 1 - 7/6`

`=` `- 7/6`

`--`

`e)` `6/7 . 8/13 + 6/7 . 9/13 - 3/13 . 6/7`

`=` `6/7 . (8/13 + 9/13 - 3/13)`

`=` `6/7 . 14/13`

`=` `12/13`

`--`

`f)` `-3/7 . 15/13 - 3/7 . 11/13 - 3/7`

`=` `-45/91 - 33/91 - 3/7`

`=` `-78/91 - 3/7`

`=` `-9/7`